FIG. 5 is a sectional view of conventional speaker 501 that includes diaphragm 31 made of thin film. Voice coil 14 is fixed to a lower surface of diaphragm 31. Yoke 8, magnet 9, and plate 10 constitute magnetic circuit 11 that has magnetic gap 11 into which a lower end of voice coil 14 is inserted.
FIG. 6 is a schematic sectional view of portable phone 502 including speaker 501. Portable phone 502 has waterproof property. Speaker 501 includes with waterproof sheet 32, made of moisture-transmissive and water proof material in order to prevent water from entering therein through set sound-radiating hole 21 and speaker sound-radiating hole 17.
If entire portable phone 502 has waterproof property, diaphragm 31 can hardly have strength enough against water entering therein, so that diaphragm 31 may be broken and encountered by water entering therein.
It is thus needed to seal sound-radiating hole 17 with a water-proof sheet made of moisture-transmissive and water proof material in order to provide speaker 501 with the waterproof property. However, the foregoing structure probably invites an abnormal sound generated by vibration of the waterproof sheet due to a sound pressure from diaphragm 31, or the sound radiated from diaphragm 31 might be blocked, thereby degrading acoustic characteristics.
On top of that, it is a cumbersome work to stick the waterproof sheet with accuracy to portable phone 502, whereby the yield can be lowered or waterproof reliability can be degraded. The waterproof sheet raises the cost of the speaker.
Conventional speakers similar to speaker 501 are disclosed in Patent Literatures 1 and 2.